Vacuum furnace equipment for heat treatment, hardening and brazing working parts

ABSTRACT

A vacuum furnace unit is provided for heat treating, hardening and brazing work pieces using a vacuum slide valve in combination with a detachable protecting dome by means of which the heat treated goods are cooled off in salt, oil, protective gas or similar media or undergo a surface treatment.

Elnited States Patent Kalbfleisch Feb. 18, 1975 1 1 VACUUM FURNACE EQUIPMENT FOR 1,876,960 9/1932 Kenworthy 266/5 R HEAT TREATMENT, HARDENING AND 25 1 S lZU 21 1 .1 BRAZIMG WORKING PARTS 2,983,600 5/1961 Blue et a1 [75] Inventor: Fritz Kalbfleisch, Lieblos, Germany 3,522,357 7/1970 Pine ct a1 13/31 [73] Assignee: Deutsche Gold-und Scheideanstalt FOREIGN PATENTS OR APPLICATIONS vormals Roessler, Frankfurt 286,860 9/1915 Germany 266/5 (Main), Germany 754,920 8/1956 Great Britain 1,084,923 7/1960 Germany 75/845 [22] Filed: Nov. 8, 1972 21 Appl 304 32 Primary Examiner-Roy Lake Assistant ExaminerPaul A. Bell Atl0rney,Agent, orFirm-Cushman, Darby and [30} Forelgn Appllcatlon Prlority Data Cushman Nov, 12, 1971 Germany 2156306 52] us. 01. ..266/5 E, 266/4 A, 13/31 ABSTRACT [51] Int. Cl C2ld 9/00 A vacuum furnace unit is provided for heat treating, [58] Field of Search 266/4 A, 4 B, 5 A, 5 B, hardening and brazing work pieces using a vacuum 266/5 C, 5 R, 6 R, 4 R; 148/13, 13.2; 23/290, slide valve in combination with a detachable protect- 277 R, 261; 75/223, 224, 225, 226, 227, ing dome by means of which the heat treated goods 84.5; 13/26, 27, 31 are cooled off in salt, oil, protective gas or similar media or undergo a surface treatmentv [56] References Cited 7 Claims, 4 Drawing Figures UNITED STATES PATENTS 1,699,784 1/1929 Fuchs 266/5 B l'llllll'lg 6-1.1

PATENIEU FEB] 8195 SHEET 3 or '3 1 VACUUM FURNACE EQUIPMENT FOR HEAT TREATMENT, HARDENING AND BRAZING WORKING PARTS There are known furnaces for the heat treatment of work pieces in which the work pieces are brought to the required temperature under vacuum (neutral enviroment) and subsequently are cooled in a protective gas atmosphere under reduced pressure or are quenched in oil. Furnace constructions of this type cannot be used if the heated goods must be quenched in a salt or water bath in order to guarantee the required properties of the material.

In the existing and partly very expensive vacuum furnaces the work pieces to be treated generally are loaded into the heating chamber of the furnace horizontally. Parts subject to deformation such as long shafts, screw conveyors, cutter bars, etc. can be heat treated in deformation free manner by these processes only when applying special precautions which, however, are not absolutely effective.

There are also known furnace units, for example, pittype furnaces, in which the goods to be heat treated are heated and cooled while hanging. In this furnace construction the work pieces are heated under a normal atmosphere or a protective gas, carburized, carbonitrited or the like and than drawn into a dome (bell) filled with-protective gas which is situated above the pit furnace. Subsequently the aforementioned dome including the heated charge is brought over an oil, water or salt bath and immersed in one of the aforementioned baths. The dome filled with protective gas prevents the highly reactive surfaces of the heated goods from coming into contact with air (oxidation) during the transfer process.

According to the present invention there is proposed a furnace construction which makes possible the heating of work pieces in a vacuum to the necessary hardening, annealing or brazing temperature. Subsequently the work pieces are transferred in the protective dome and quenched in a salt, water or oil bath. Furthermore, accessory equipment for washing, drying and surface protection can be incorporated. It was found that although the bell filled with protective gas is open at the bottom during the transfer process there was no contact with air of the charge heated under vacuum.

The invention will be understood best in connection with the drawings wherein FIG. 1 is a sectional view of the vacuum furnace according to the invention;

FIG. 2 illustrates one way of transferring the bell into quenching positions; and

FIG. 3 illustrates another way of transferring the bell into quenching positions.

As shown in FIG. 1 the heat treatment is carried out with an apparatus indicated generically at consisting of a vertical, water cooled, vacuum vessel 1 in which there is located the electrically heated furnace 2 and an intermediate piece 3 which includes a horizontal vacuum slide valve 4. The vacuum slide valve is operated by the driving mechanism 5 to open and close the vacuum vessel.

The removable and water cooled vacuum or protective bell 6 is equipped with a lifting and lowering mechanism 7 on which there is hung the charging support 22 and the charge (or work piece) 8 and 8. The protective bell 6 can also be provided with an insulation 9 if LII the heated goods should not undergo any reduction in temperature during the transfer process. The dome 6 can also be provided with a fan 10 which permits work pieces in the dome to cool under a non-oxidizing protective gas, e.g. nitrogen or argon, without the transfer process. The insulated lid 11 serves to close the annealing furnace 2 during the heating period and the radiation shields 12 provide a high temperature uniformity in the working space of the furnace 2.

The vacuum pump 13 and valves 14, 15 and 16 are shown schematically. Generally there is used for heating the furnace installation graphite or molybdenum heaters. These heaters allow very high operating temperatures and a high power concentration (very short heating up time).

Under these prerequisites the proposed apparatus operates as follows.

The vacuum furnace with the vacuum slide valve 4 in the closed position is evacuated and heated up to the operating temperature. During this period the bells can be charged or already positioned above the vacuum furnace with the work load in the raised position 8. Simultaneously or subsequently the protective dome 6 is also evacuated. After the annealing furnace has reached the desired temperature, the vacuum slide valve 4 is opened and the work load to be treated brought from position 8 into position 8'. The annealing furnace is closed during the heating cycle by the insulated lid 11. Work pieces sensitive to shock heating should be heated up in position 8 together with the furnace. After the goods to be annealed are brought to temperature and are held for a correspondingly long time at the temperature (soaking time), they are brought into position 8 by the lifting mechanism 7, the vacuum slide valve 4 is closed and the protective dome 6 flooded with a protective gas, e.g. nitrogen or argon. Following this the protective dome with the heated goods can be brought to the corresponding quenching or treating stations according to different systems, as shown for example in FIGS. 2 and 3, and the charge lowered.

It should be understood that is is also possible to carry out the transfer operation under vacuum. In this case a second vacuum slide valve 17 such as that designated 4, must close in a reverse manner the opening of the protective dome during the transfer process. If cooling is carried out under vacuum or partial pressure of a protective gas, then there must be provided at the corresponding cooling stations the necessary vacuum or protective gas supply devices.

For example in FIGS. 2 and 3 the dome with the heated work piece in position I can be moved to position II where it is placed in a salt bath, or can be moved to position III where the work piece is immersed in an oil bath or is moved to position [V where it is immersed in a water bath, etc.

I claim:

1. In combination a vacuum furnace unit for heat treating, hardening and brazing of work pieces, a removable protective dome for said furnace, a vacuum slide valve operatively connected to said furnace, means in said dome for supporting the work pieces inside said dome, means in said dome for raising and lowering said supported work pieces to position out of and in said furnace and separate treating means for receiving said work pieces while external to, but supported by, said dome and while out of said furnace.

furnace is provided with a retractable insulated lid with additional radiation shields to prevent a temperature fall within the working space of the furnace.

6. A combination according to claim 1 wherein there are a plurality of said separate treating means arranged axially.

7. A combination according to claim 1 wherein there are a plurality of said separate treating means arranged radially.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 9 Dated Fe ruary 1 1975 Inventor(s) FRITZ KALBFLEISCH It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the patent heading the Assignee's name should be given as follows;

-Deutsche Goldund Silber-Scheideanstalt vormals Roessler-- Signed and sealed this 6th day of May- 1.975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 9 Dated February 975 Inventor(s) FRITZ KALBFLEISCH It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the patent heading the Assignee's name should be given as follows:

--Deutsche Goldund Silber-Scheideanstalt vormals Roessler-- Signed and sealed this 6th day of May 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. In combination a vacuum furnace unit for heat treating, hardening and brazing of work pieces, a removable protective dome for said furnace, a vacuum slide valve operatively connected to said furnace, means in said dome for supporting the work pieces inside said dome, means in said dome for raising and lowering said supported work pieces to position out of and in said furnace and separate treating means for receiving said work pieces while external to, but supported by, said dome and while out of said furnace.
 2. A combination according to claim 1 wherein said slide valve is moveable horizontally and is positioned between said furnace and said dome.
 3. A combination according to claim 2, wherein said furnace is provided with a retractable insulated lid with additional radiation shields to Prevent a temperature fall within the working space of the furnace.
 4. A combination according to claim 1 wherein a second vacuum slide valve is connected to said dome and is adapted to close the opening therein.
 5. A combination according to claim 4 wherein said furnace is provided with a retractable insulated lid with additional radiation shields to prevent a temperature fall within the working space of the furnace.
 6. A combination according to claim 1 wherein there are a plurality of said separate treating means arranged axially.
 7. A combination according to claim 1 wherein there are a plurality of said separate treating means arranged radially. 